NEW DELHI — Two bombs planted on bicycles killed at least 13 people and wounded some 70 in a busy shopping district in the southern India city of Hyderabad at the height of Thursday’s evening rush hour, the largest terrorist bombing in the country since September 2011.

Sushil Kumar Shinde, India’s home affairs minister, said the central government had warned state governments that such an attack was planned.

“We have had some information for the last two days of such an incident,” he said.

Hyderabad, one of India’s largest cities and a leading center of the country’s burgeoning pharmaceutical and biotechnology industries, has suffered other such attacks in recent years, usually linked to sectarian friction.

The blast sites Thursday — in the Dilsukh Nagar neighborhood, packed with shops, restaurants, theaters and a huge produce market — were mobbed by protesters, reporters, the curious, and politicians and their large security contingents. Television news footage in the hours afterward showed chaotic scenes, with some investigators trying to find the remains of explosive devices while huge numbers of people jostled for space around them.

Shinde, speaking to journalists in New Delhi, said that the bicycles were 150 meters away from each other and the bombs detonated about 10 minutes apart, killing eight at one site and three at the other. But he warned that the toll could rise, and it did so, with 13 reported dead by midnight.

In a Twitter message, Prime Minister Manmohan Singh said. “This is a dastardly attack, the guilty will not go unpunished.”

Officials sought to diminish the chances of the kind of sectarian rioting that has long plagued the country.

Asked in a news conference if he believed that Muslim extremists were to blame for the bicycle blasts, Shinde said: “We have to investigate. We should not come to conclusions immediately.”

Singh, in another Twitter message, said, “I appeal to the public to remain calm and maintain peace.”

Asaduddin Owaisi, a Muslim member of Parliament from Hyderabad, called the blasts “cowardly.”

“I feel that the priority is to maintain peace,” he said. “Let us not fall prey to rumors.”